Transdermal nitroglycerin patches are used mainly in the therapy of angina pectoris. However, the magnitude and duration of their effects are still controversial. In this study, transdermal discs with nitroglycerin were given to 14 patients with acute myocardial infarction (AMI) and mild hemodynamic impairment. Seven patients received Nitroderm TTS, and seven patients Deponit 5 (in this case 2 patches), the nitroglycerin dose being 10 mg. Hemodynamic measurements were made 19-24 h after application of the patch and 1 h after its removal. Comparing with the values obtained 1 h after removal of the patch, 19-24 h after the application of the patch heart rate was significantly higher (90.2 +/- 3.8 vs. 85.6 +/- 4.0 min-1; p less than 0.01), mean right atrial pressure was significantly lower (10.8 +/- 1.0 vs. 12.7 +/- 1.3 mm Hg; p less than 0.01), and so were the pulmonary artery pressure: systolic (36.9 +/- 3.0 vs. 43.0 +/- 3.1 mm Hg; p less than 0.001), mean (26.8 +/- 2.1 vs. 31.4 +/- 2.0 mm Hg; p less than 0.001) and the capillary wedge pressure (19.2 +/- 1.8 vs. 23.0 +/- 1.9 mm Hg; p less than 0.01). These findings revealed that in patients with AMI hemodynamic effects persist for at least 19 h after single application of a nitroglycerin patch of 10 mg. The therapy is safe and the risk of side effects is small.